1. Field of the Invention
The present invention relates to methods for making shape memory alloy products (e.g., clasp, biological implant, sensor, socket, clip, switch, eyeglass frame, etc.).
2. Description of the Related Art
FIG. 5 shows a conventional method of manufacturing TiNi shape memory alloy product. As shown in FIG. 5, TiNi shape memory alloy is manufactured by the ordinary metallurgical processes of melting, hot forging, and rolling. Raw materials (e.g., sponge Ti and Ni pellets) are melted at 1,350 to 1,500° C. by a melting furnace (e.g., high-frequency vacuum induction melting furnace, arc melting furnace, or plasma-melting furnace). After the raw materials are melted, they undergo forging and rolling, and then is formed into a primary product (e.g., sheet or wire) through cold working. The primary product is machined and formed into the shape of the final product. Then, in order to get a shape memory effect or super-elasticity, a shape memory heat treatment is applied to the product that is formed into the shape of the final product. In the shape memory heat treatment, for example, the product is heated and held at a temperature of between 300 and 600° C. for several minutes to an hour, and is then cooled.
Further, Japanese Laid-open Patent Publication No. 11-106880 describes a method for manufacturing a shape memory alloy product. In this known manufacturing method, raw materials (e.g., sponge Ti and Ni pellets) for a shape memory alloy are melted and formed into an ingot. This ingot is then melted and cast using a casting mold. After the casting is finished, the cast alloy together with the casting mold is heated in a heating furnace (i.e., undergoes shape memory heat treatment). When the heat treatment is finished, the casting mold is removed. With this method, in order to get a super-elastic effect, the shape memory heat treatment must be applied while the cast alloy is constrained inside the casting mold.